1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a columnar spacer and a manufacturing method thereof.
2. Discussion of the Related Art
A liquid crystal display (LCD) device is driven based on the optical anisotropy and polarization characteristics of a liquid crystal material. In general, the LCD device includes two substrates spaced apart and facing each other with a liquid crystal material layer interposed between the two substrates. Each of the substrates includes respective electrodes facing each other such that a voltage applied to each electrode induces an electric field between the electrodes perpendicular to the substrates. An alignment of liquid crystal molecules of the liquid crystal material layer changes by varying an intensity or direction of the applied electric field. Accordingly, the LCD device displays an image by varying light transmittance through the liquid crystal material layer in accordance with the arrangement of the liquid crystal molecules.
FIG. 1 is an expanded perspective view illustrating a related art LCD device. As shown in FIG. 1, the LCD device 11 includes an upper substrate 5, referred to as a color filter substrate, and a lower substrate 22, referred to as an array substrate, having a liquid crystal layer 14 interposed therebetween. On the upper substrate 5, a black matrix 6 and a color filter layer 8 are formed in a shape of an array matrix including a plurality of red (R), green (G), and blue (B) color filters surrounded by corresponding portions of the black matrix 6. Additionally, a common electrode 18 is formed on the upper substrate 5 to cover the color filter layer 8 and the black matrix 6.
On the lower substrate 22, a plurality of gate lines 13 perpendicularly cross a plurality of data lines 15 to define a matrix. A plurality of thin film transistors (TFTs) T are positioned such that each TFT T is located at a respective intersection of one of the gate lines 13 and one of the data lines 15. Furthermore, a plurality of pixel electrodes 17 are formed on respective pixel regions P defined between the gate lines 13 and the data lines 15 of the lower substrate 22. The pixel electrode 17 includes a transparent conductive material having high transmittance, such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).
As further shown in FIG. 1, a storage capacitor CST is disposed in each pixel and connected in parallel to the pixel electrode 17 of the pixel. The storage capacitor CST comprises a portion of the gate line 13 as a first capacitor electrode and a metal pattern 30 as a second capacitor electrode. Since the metal pattern 30 is connected to the pixel electrode 17 through a contact hole, the storage capacitor CST is electrically contacted to the pixel electrode 17. The metal pattern 30 may be made of the same material as the data line 15. When fabricating the LCD device 11 of FIG. 1, the upper substrate 5 is aligned with and attached to the lower substrate 22.
Although not shown in FIG. 1, spacers are formed between the first and second substrates to maintain a uniform cell gap. The spacers may be spherical spacers, which are sprayed on one of the upper and lower substrates 5 and 22, or columnar spacers, which are directly patterned on one of the upper and lower substrates 5 and 22.
FIG. 2 is a cross-sectional view of the related art liquid crystal display (LCD) device and corresponds to a cross-section along the line II-II of FIG. 1. The related art LCD device includes a columnar spacer.
As shown in FIG. 2, the related art LCD device includes an upper substrate 5, a lower substrate 22, and a liquid crystal layer 14. The upper and lower substrates 5 and 22 are spaced apart from each other with the liquid crystal layer 14 interposed therebetween.
A pixel region P including a switching region S and a storage region ST are defined on the lower substrate 22. A thin film transistor T is formed in the switching region S and comprises a gate electrode 32, an active layer 34, a source electrode 36 and a drain electrode 38. A storage capacitor CST is formed in the storage region ST and comprises a portion of a gate line 13 as a first capacitor electrode and a metal pattern 30 as a second electrode. The metal pattern 30 has an island shape and overlaps the portion of the gate line 13. The metal pattern 30 contacts the pixel electrode 17. The storage capacitor CST may have various structures and shapes. A passivation layer 40 is formed on the thin film transistor T and the storage capacitor CST. A transparent pixel electrode 17 is formed on the passivation layer 40 in the pixel region P and is connected to the drain electrode 38.
In FIG. 2, the upper substrate 5 is spaced apart from the lower substrate 22. On an inner surface of the upper substrate 5, a black matrix 6 is disposed in the position corresponding to the thin film transistor T, the gate line 13 and a data line 15 of FIG. 1. The black matrix 6 is formed on the entire surface of the upper substrate 5 and has openings corresponding to the pixel electrode 17 of the lower substrate 11, as shown in FIG. 1. The black matrix 6 prevents light leakage in the LCD device except for the portion for the pixel electrode 17. The black matrix 6 protects the thin film transistor T from the light such that the black matrix 6 prevents generating of photo current in the thin film transistor T. A color filter layer including color filters 8a, 8b and 8c is formed on the inner surface of the upper substrate 5 to cover the black matrix 6. Each of color filters 8a, 8b and 8c has one of the red, green, and blue colors and corresponds to one pixel region P where the pixel electrode 17 is located. A common electrode 18 formed of a transparent conductive material is disposed on the color filter layer 8a, 8b and 8c over the upper substrate 5.
Here, a columnar spacer 20 is formed between the upper and lower substrates 5 and 22 and corresponds to the thin film transistor T. The columnar spacer 20 may be formed on one of the upper and lower substrates 5 and 22.
A method of forming a columnar spacer according to the related art will be explained hereinafter with reference to attached drawings. FIGS. 3A to 3D illustrate processes of forming a columnar spacer according to the related art.
As illustrated in FIG. 3A, photosensitive resin is coated on a substrate 50, thereby forming a photosensitive layer 52. The photosensitive resin may be photoresist, which is used in a photolithographic process. The photosensitive resin may be a positive type, in which a portion exposed to light is developed and removed, or a negative type, in which a portion not exposed to light is developed and removed.
Next, as illustrated in FIG. 3B or FIG. 3C, a mask M is disposed over the photosensitive layer 52. The mask M includes a transmitting portion B1 and a blocking portion B2. Here, the photosensitive layer 52 of FIG. 3B is a positive type, and the photosensitive layer 52 of FIG. 3C is a negative type. In FIG. 3B, the blocking portion B2 of the mask M corresponds to a region for forming a columnar spacer. In FIG. 3C, the transmitting portion B1 of the mask M corresponds to the region for forming the columnar spacer.
Subsequently, the photosensitive layer 52 is exposed to light through the mask M and is developed. Therefore, as illustrated in FIG. 3D, a columnar spacer 54 is formed in a desired region. As stated above, the columnar spacer 54 may be formed on the array substrate or the color filter substrate.
However, to form the columnar spacer, an additional photolithographic process is required after manufacturing the array substrate or the color filter substrate. Moreover, since more than 95% of the photosensitive layer is removed, materials are wasted, thereby increasing costs.